EP0040114B1 - Système optique d'observation en temps réél à balayage - Google Patents

Système optique d'observation en temps réél à balayage Download PDF

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Publication number
EP0040114B1
EP0040114B1 EP81400591A EP81400591A EP0040114B1 EP 0040114 B1 EP0040114 B1 EP 0040114B1 EP 81400591 A EP81400591 A EP 81400591A EP 81400591 A EP81400591 A EP 81400591A EP 0040114 B1 EP0040114 B1 EP 0040114B1
Authority
EP
European Patent Office
Prior art keywords
wave
medium
sweeping
detector
interaction
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP81400591A
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German (de)
English (en)
French (fr)
Other versions
EP0040114A1 (fr
Inventor
Jean-Pierre Huignard
Marcel Malard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
OFFERTA DI LICENZA AL PUBBLICO
Original Assignee
Thomson CSF SA
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Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0040114A1 publication Critical patent/EP0040114A1/fr
Application granted granted Critical
Publication of EP0040114B1 publication Critical patent/EP0040114B1/fr
Expired legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F2/00—Demodulating light; Transferring the modulation of modulated light; Frequency-changing of light
    • G02F2/002—Demodulating light; Transferring the modulation of modulated light; Frequency-changing of light using optical mixing
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
    • G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/20—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from infrared radiation only

Definitions

  • the invention relates to the field of optical detection and imaging of large objects, and more specifically relates to an optical system for real-time observation, taking advantage, to amplify the signal to be detected, of the possibility that some media have to generate a complex wavefront in real time.
  • the object of the invention is to improve the detection and imaging of large and / or distant objects.
  • the known observation and detection devices generally comprise a light source making it possible to illuminate the object to be detected by means of an illumination device sending the energy radiated by the source onto the object.
  • the illuminated object returns at least part of the received radiation to a detection device comprising, inter alia, a collecting optic intended to form an image of the illuminated object on a detector, photosensitive support, photodetector, mosaic of photodetectors, vi- dicon ...
  • heterodyne detection is a known technique for improving the signal-to-noise ratio (Proceedings of the International Conference on Laser 78, December 11-15, 1978, T. Oimeara, page 546, last paragraph).
  • the two or three-dimensional object to be observed is illuminated, point by point, or small area by small area, by scanning an illumination beam substantially focused on the mean plane of the 'object.
  • the beam re-emitted at each instant is taken up and sent to a detection device which, associated with a display screen, makes it possible finally to obtain a two-dimensional image of the object.
  • This system also comprises an interaction medium as described above for obtaining the reinforcement of the optical signal to be detected.
  • the subject of the invention is an optical system for real-time observation of an object comprising a coherent radiation source, providing a concentrated beam of radiant energy illuminating an object, a pumping beam and an interaction medium, the beam from the object and the pumping beam interfering in this interaction medium in which the spatial modulation of light intensity resulting from the interference fringes induces a spatial modulation of the refractive index, the network of photoinduced strata diffracting a fraction of the pump wave in the form of an isomorphic wave front from that emanating from the object, the wave coming from the object therefore being amplified, characterized in that it comprises in addition to a deflecting device which ensures the scanning of the object by means of the concentrated beam, the radiation coming from the object being transmitted by a reverse return via the deflecting device to go and interfere in this medium, optical means for heterodyne detection of the radiation emerging from the illuminated zone of the object after crossing the interaction medium, these means comprising a point detector, means for displaying an image of the object whose scanning is in synchron
  • the system according to the invention implements the reproduction of a wavefront of complex morphology, generated by the interference, in an interaction medium, of an incident optical wave having this wavefront with a wave pump.
  • This interference occurs in a three-dimensional medium, shown schematically at 1 in FIG. 1, and whose physical characteristics and in particular the refractive index, are spatially modulated by a network of fringes 11 resulting from the interference of the incident optical wave 12 of wavefront k a and the pump wave 13, wave front Sp i , plane for example. Due to the existence of this spatial modulation which induces a network of strata by gradient, a fraction of the energy of the pumping wave is diffracted in the form of an emerging wave 14, with wave front k ' it with characteristics isomorphic to those of the incident wave, part of which emerges from the medium along the wavefront E o , unchanged.
  • the wave ⁇ ' i propagates in the same direction as the wave k o , as indicated by the small arrows associated with these wave fronts, in fig. 1.
  • Another fraction of the energy of the pump wave 13 crosses the medium 1 and exits according to the beam 15. By interposing on its path and normally to this, a reflecting mirror 16, this wave 15 is returned to the medium 1.
  • Part of the energy is diffracted by the network of strata inscribed in the medium in the form of an emerging wave of complex wavefront ⁇ * i , conjugate of the wave ⁇ o ⁇ ⁇ * i has isomorphic characteristics of those of E o , but follows its trajectory in opposite direction, as indicated by the small arrows in fig. 1.
  • ⁇ i * returns to the object from which ⁇ o emanates.
  • the time constant ⁇ varies from 10 -3 to 10 -12 seconds.
  • Variations in the network of fringes can be induced by variations in the incident wave, due for example to a scanning of the object, or a frequency offset between the incident wave and the pump wave, the operating condition. of the device is that these variations are slow compared to the time constant T : the network of mobile strata must be able to be effectively established in the interaction medium.
  • the registration of the dynamic hologram requires high power densities on the pump beam, from 10 MWcm -2 to 1 kWcm- 2 .
  • the index modulation results from the simultaneous presence of a space charge effect and the linear electrooptic effect (photorefractive effect).
  • the two or three-dimensional object to be observed is illuminated, point by point, or small area by small area, by scanning an illumination beam substantially focused on the mean plane of the 'object.
  • the beam re-emitted at each instant is taken up and sent to a detection device which, associated with a display screen, makes it possible finally to obtain a two-dimensional image of the object.
  • This system also comprises an interaction medium as described above to obtain the reinforcement of the signal to be detected.
  • a first embodiment of this system is shown diagrammatically in FIG. 3.
  • a laser 2 sends a parallel beam of coherent light onto the semi-reflecting plate 3 which divides it into an illumination beam 5 from the object 20, and a pumping beam 6.
  • the illumination beam from the object is deflected by the mirror 4 on a beam expander 7, undergoes an enlargement there and arrives on a semi-reflecting plate 9 which sends it on an XY deflector 10, comprising a conventional component such as a galvanometric mirror or a tank acousto-optics. It is then taken up by a focusing optic 21, the focal plane of which is substantially on the object 20 to be detected, and at a given instant, the lighting beam illuminates a point A of the object.
  • This point re-emits light constituting a beam which, by reverse return, crosses the optic 21 and the deflector 10 which centers it on the optical axis of the system.
  • This beam emerging from the object crosses the semi-transparent plate 9 and arrives at the interaction medium 1.
  • the pumping beam 6, reflected by the semi-reflecting plate 3 is widened by means of the beam expander 8 and arrives at the interaction medium 1.
  • the interaction of the object beam and the pumping beam induces a network of strata.
  • a fraction of the energy of the pump wave is diffracted in the form of a emergent wave ⁇ ' o with characteristics isomorphic to those of the object wave k o which emerges from the medium 1, unchanged. Everything happens as if the 2 o wave was amplified.
  • the beam to be detected containing the energy of E o and E ' o, is focused on the detector 23 placed in the focal plane of a collecting optic 22.
  • the detected signal is displayed on a television-type display screen 24, the scanning of which is synchronous with the deviator XY. To ensure this synchronism, it is the same oscillator XY, 25, which controls the scanning of the screen and the deflector. A two-dimensional image of the object 20 is obtained on the screen.
  • the wave to be detected and a wave coming from a local oscillator, which is slightly shifted in frequency, are made to interfere on a quadratic detector.
  • the signal to noise ratio is improved compared to a homodyne detection as described above.
  • the replica wave kann ' o is played the role of the wave coming from the local oscillator.
  • This wave ⁇ ' o is perfectly isomorphic of the object wave to be detected for all the points of the wave front, whatever its shape.
  • FIG. 4 An observation system with heterodyne detection is shown in FIG. 4.
  • the beam diffracted by the illuminated point of the object at a given time crosses the deflector which centers it on the optical axis of the system, and arrives in the interaction medium 1.
  • the device 41 here an acousto-optical tank, interposed between the beam expander 8 and the interaction medium 1.
  • the interference of these two waves in this medium inscribes a network of strata which causes the diffraction of a wavefront beam ⁇ ' 0 , replica of ⁇ o .
  • These two waves ⁇ ' o and E o slightly offset in frequency then come to interfere, through the optics 22, on the quadratic detector 42, where the signal is analyzed around the difference frequency between the two waves.
  • This detector generates an electrical signal ip h displayed on the television-type screen 24 scanned in synchronism with the deflector 10 using the oscillator 25. This gives a two-dimensional image of the object on the screen.
  • the conjugate wavefront emerges from the medium and propagates in the direction from which the object wave originates, being at each point of its isomorphic trajectory from the object wavefront at this point.
  • this conjugate wave therefore returns towards the object and reinforces the illumination of point A from which the object wave having served to generate it came, which makes this point brighter, and can in certain cases, a detailed observation of this point, with stop of the scanning on this point, and analysis by a composite detector.
  • This conjugate wave is also diffracted by the object, at least in part, in the direction of travel of the initial object wave and contributes to strengthening it.
  • FIG. 5 An exemplary embodiment of the system using this recovery is shown in FIG. 5. This example concerns an observation system with heterodyne detection.
  • a laser 2 supplies the total optical energy of the system. It emits a parallel beam separated into a beam 5 for lighting the object and a pumping beam 6, by the semi-transparent blade 3.
  • the beam for lighting the object, deflected by the mirror 4 and widened by the beam expander 7 is sent to the deflector 10 via the semi-transparent blade 9.
  • optics 21 Focused by optics 21 whose focal plane is located substantially on the object 20, which is not necessarily plane, it illuminates, at a given moment a point A, or a small region around A, depending on the shape of the object at this point.
  • the illuminated point is in a hollow in the object and the beam 5 illuminates a small portion of this hollow.
  • the illuminated point, or the small illuminated area re-emits radiation, at least part of which, by reverse return crosses optics 21, deflector 10 and arrives, along the axis of the optical system, on interaction medium 1, with a wave front ⁇ o depending on the shape of the illuminated "point" and possibly on index inhomogeneities of the medium crossed.
  • the pumping beam 6, widened by the expander 8 passes through the acousto-optic tank 41 and also arrives in the medium 1.
  • the two beams, object and pump interact, at least partially, in this medium and induce a network of strata which diffracts part of the pumping beam according to a wavefront wave ⁇ ' o , replica of ⁇ o , in the direction of propagation of E o .
  • ⁇ ' o plays the role of wave generated by the local oscillator for the heterodyne detection of the object.
  • the two waves ⁇ o and ⁇ ' o interfere on the detector 42, where they are focused by the lens 22.
  • the detector which advantageously analyzes the signal around the difference frequency of the two waves generates a signal ip h which is displayed on the television type screen 24, the scanning of which is synchronous with the deflector XY 10; the synchronism of the scans is obtained by controlling them by the same oscillator 25.
  • This beam fraction is returned to the medium by interposing on its path the mirror 51.
  • a part of it emerges according to a complex wave, combined with the incident object wave, with a wave front E * o .
  • This wave ⁇ * o propagates in the opposite direction from ⁇ o , and therefore returns to the object, with a wave front identical at each point of its trajectory to the wave front E o coming from the object, and undergoing possibly in opposite direction, all the deformations undergone by ⁇ o .
  • This conjugate wave ⁇ * o therefore arrives on the object, at the “point” from which E o originates, and brings additional lighting to this “point”, supplement which can be very substantial, taking into account that this conjugate wave , depending on the effectiveness of the interaction, can be much more intense than the actual object wave.
  • This lighting reinforcement can allow direct observation, for example with the eye, of the whole object, of a part or of a point of the object, according to the amplitude of the scanning which can, precisely, be stopped. to see a specific point on the object.
  • This additional radiation also leaves, at least in part, towards the detection system, and contributes to reinforcing the object wave E o .

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Remote Sensing (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Nonlinear Science (AREA)
  • Optics & Photonics (AREA)
  • Electromagnetism (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Holo Graphy (AREA)
EP81400591A 1980-05-08 1981-04-14 Système optique d'observation en temps réél à balayage Expired EP0040114B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8010245 1980-05-08
FR8010245A FR2482325A1 (fr) 1980-05-08 1980-05-08 Systeme optique d'observation en temps reel a balayage

Publications (2)

Publication Number Publication Date
EP0040114A1 EP0040114A1 (fr) 1981-11-18
EP0040114B1 true EP0040114B1 (fr) 1984-10-03

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ID=9241741

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81400591A Expired EP0040114B1 (fr) 1980-05-08 1981-04-14 Système optique d'observation en temps réél à balayage

Country Status (6)

Country Link
US (1) US4442455A (enrdf_load_stackoverflow)
EP (1) EP0040114B1 (enrdf_load_stackoverflow)
JP (1) JPS574025A (enrdf_load_stackoverflow)
CA (1) CA1174494A (enrdf_load_stackoverflow)
DE (1) DE3166412D1 (enrdf_load_stackoverflow)
FR (1) FR2482325A1 (enrdf_load_stackoverflow)

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FR2508664B1 (enrdf_load_stackoverflow) * 1981-06-30 1985-07-19 Thomson Csf
FR2516232B1 (fr) * 1981-11-09 1986-02-21 Thomson Csf Interferometre de type michelson a miroir photorefractif
FR2517839A1 (fr) * 1981-12-07 1983-06-10 Thomson Csf Dispositif de detection heterodyne d'une image optique
FR2528993A1 (fr) * 1982-06-18 1983-12-23 Thomson Csf Dispositif d'eclairement d'un milieu electro-optique pour enregistrer des hologrammes en temps reel
US4549212A (en) * 1983-08-11 1985-10-22 Eastman Kodak Company Image processing method using a collapsed Walsh-Hadamard transform
US4877965A (en) * 1985-07-01 1989-10-31 Diatron Corporation Fluorometer
USRE34782E (en) * 1985-07-01 1994-11-08 Diatron Corporation Fluorometer
FR2594233A1 (fr) * 1986-02-07 1987-08-14 Morand Christian Dispositif d'analyse et de visualisation en couleurs d'objets eventuellement masques par un ecran
US4796992A (en) * 1986-12-11 1989-01-10 Hamamatsu Photonics Kabushiki Kaisha Apparatus for optically analyzing an object using four-wave mixing technique
JPS63155130A (ja) * 1986-12-19 1988-06-28 Hamamatsu Photonics Kk 光波面を観測する装置
US5072127A (en) * 1987-10-09 1991-12-10 Pressco, Inc. Engineered video inspecting lighting array
US4882498A (en) * 1987-10-09 1989-11-21 Pressco, Inc. Pulsed-array video inspection lighting system
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GB8807030D0 (en) * 1988-03-24 1988-04-27 Ciba Geigy Ag Preparing hologram
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US4896150A (en) * 1988-04-18 1990-01-23 Brotz Gregory R Three-dimensional imaging system
FR2638852B1 (fr) * 1988-11-09 1990-12-28 Telecommunications Sa Dispositif de detection d'un signal optique coherent
JPH0378609A (ja) * 1989-08-23 1991-04-03 Brother Ind Ltd 光スキッド式表面粗さ計測装置
JPH0621868B2 (ja) * 1989-09-26 1994-03-23 新技術事業団 ヘテロダイン検波結像系及び該結像系を用いた光断層像画像化装置
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US5233554A (en) * 1990-09-10 1993-08-03 United Technologies Corporation Programmable optical correlator
US5120133A (en) * 1990-12-21 1992-06-09 United States Of America Is Represented By The Secretary Of The Navy Interferometer with two phase-conjugate mirrors
US5172005A (en) * 1991-02-20 1992-12-15 Pressco Technology, Inc. Engineered lighting system for tdi inspection comprising means for controlling lighting elements in accordance with specimen displacement
US5203339A (en) * 1991-06-28 1993-04-20 The Government Of The United States Of America As Represented By The Secretary Of The Department Health And Human Services Method and apparatus for imaging a physical parameter in turbid media using diffuse waves
FR2696014B1 (fr) * 1992-09-18 1994-11-04 Thomson Csf Miroir à conjugaison de phase.
AT399222B (de) * 1992-10-19 1995-04-25 Tabarelli Werner Interferometrische einrichtung zur messung der lage eines reflektierenden objektes
US5416582A (en) * 1993-02-11 1995-05-16 The United States Of America As Represented By The Department Of Health And Human Services Method and apparatus for localization and spectroscopy of objects using optical frequency modulation of diffusion waves
US5440338A (en) * 1993-05-11 1995-08-08 Spiricon, Inc. Method and apparatus for improving dimensional measurements made with video cameras
FR2755516B1 (fr) 1996-11-05 1999-01-22 Thomson Csf Dispositif compact d'illumination
FR2783385B1 (fr) * 1998-09-15 2000-12-08 Thomson Csf Imageur actif a detectivite amelioree
FR2819061B1 (fr) * 2000-12-28 2003-04-11 Thomson Csf Dispositif de controle de polarisation dans une liaison optique
US7286993B2 (en) * 2002-01-31 2007-10-23 Product Discovery, Inc. Holographic speech translation system and method
FR2860291B1 (fr) * 2003-09-26 2005-11-18 Thales Sa Dispositif capteur de vitesse de rotation interferometrique a fibre optique

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Also Published As

Publication number Publication date
US4442455A (en) 1984-04-10
FR2482325B1 (enrdf_load_stackoverflow) 1983-11-25
CA1174494A (en) 1984-09-18
DE3166412D1 (en) 1984-11-08
EP0040114A1 (fr) 1981-11-18
JPS574025A (en) 1982-01-09
FR2482325A1 (fr) 1981-11-13

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